Magnetic chuck



J. E. SEDERHOLM MAGNETIC CHUCK Filed August 2 1924 rolffz MIM" il O

Patente-d Nov. 3Q, 1926.

ENQ.

FATELNT JCI-IN E. SEDERHOLM, OF ST. PAUL, MNNESOTA, ASSIGNOR TO AMERICANHOIST @s DERRICK CO., A PARTNERSHIP COIYIPOSED OF F. J. JOHNSON AND W.0. WASHBURN,

F BAMSEY COUNTY, MINNESOTA.

MAGNETIC CHUCK.

Application filed August 2, 1924.

This invention relates to new and useful improvements in magnetic chucksdesigned particularly to hold and support a plurality of metallicarticles such as castings, and the like, while being ground or machined,and more particularly relates to such chucks adapted to be mounted uponthe usual reciprocating work table of an ordinary surface grinder,thereby to securely hold the work while being ground and finished.

Magnetic chucks, of ordinary construction, and such as are commonlyemployed at present, are not well adapted for use with surface grindersas a result of the prevalent danger of short-circuiting the coils orwindings mounted therein, usually caused by water entering the chuckbody and reaching the coils, it being necessary to have constant streamof water fiowing over the work and grinding 'wheel of such a machineduring the grinding operation. Magnetic chucks, to be successfully usedin connection with surface grinders, must necessarily be of water-proofconstruction so as to positively prevent any water or moisture fromentering the casing or body thereof and reaching the coils with theresultant short-circuiting and burning out of such coils.

The novel construction of the magnetic chuck features in this inventionis such that it will be impossible for any water or moisture to enterthe body and short-.circuit the coils. lt is also designed so as toreduce to a minimum the magnetic leakage. The construction of the chuckis very simple and is such that it may readily be mounted upon the usualwork table of a grinder, in either a horizontal or vertical position. 1tis pref- Virably provided with two complete magnetic circuits, therebyadapting it .to hold and support a plurality of both large and smallpieces of work for machining in one operation. The interior of the chuckis filled with a suitable insulating medium such as oil .which functionsto completely and thoroughly insulate the coils from all conductivematerial. The oil also functions to prevent moisture from entering thechuck-body and also to prevent the chuck from heating when in continuousoperation.

The particular object of this invention therefore is to provide apowerful magnetic chuck of improved and simple construction, which maybe etiiciently used 'in conjunction Serial No. 729,806.

with an ordinary surface grinder or similar device, without the usualdanger of water entering the chuck body and thus causing the coils orwindings therein to short-circuit and burn out. l i

Q A further and more specific object of the invention is to provide sucha device having an oil gauge or receptacle mounted thereon which is incommunication with the interior ofthe chuck body to allow for expansionand contraction of the insulating medium, and which gauge is alsolocated at a point above the chuck body so as to create a slightinternal pressure therein, so that in case of a leak in the chuck bodythe oil will ooze or leak out, thereby preventing water from enteringthe chuck with the resultant ruination of the coils and windings.

Other objects of the invention will more fully appear from the followingdescrip tion and the accompanying` drawings and will be pointed out inthe annexed claims.

In the drawings' there has been disclosed a structure designed to carryout the various objects of the invention but it is to be understood thatthe invention is not confined to the exact features shown as variouschanges may be made within the scope of the claims which follow.

In the accompanying drawings forming part of this specification,

Figure 1 is a view in side elevation of a, portion of an ordinarysurface grinder showing the improved chuck operatively mounted thereon;

Figure 2 is an enlarged plan view of the chuck removed from the grinder;

Figure 3 is a cross-sectional view on the line 3-3 of Figure 2;

Figure 4 is a similar view on the line 4 4 of Figure 2.-

Figure 5 is a detail sectional view showing the .connection of thereservoir with chuck chambers, and illustrating the adjustability of thereservoir.

The body of the novel chuck shown in the accompanying drawings comprisesa rectangular metallic frame having end walls 11 and 12 and the sidewalls 18 and 14. A; relatively smaller frame comprising end walls 15 and16 and side walls 17 and 18, is mounted within the larger frame as shownin Figures 2, 3 and 4. These two frames are secured to a metallic baseplate 19 by means Figure S.

of screws 2l as shown in Figures 3 and 4. A bar 22, preferably oil*Ilarger cross Section than the sections or the two frames, is centrallymounted within the smaller rectangular 'tram-e yand in l.ine manner issecured to the plate 19 by means oi similar screws 2l. The walls. oi"the two rectangular frames and also oit the bnr 22 mounted within thesmaller trame constitute the positive and negative poles or the chuck.ln the operation ot the chuck these poles will be energized to a* octthe articles placed in conT tact therewith as will be hereinafterdescribed The means provided. lor enereizing or magnetizing the negativand positive poles of theV chuck prerera` -I consists in the mountingor' a series of the space profided betr! en the valls oi' the two amesvand yalso tl e space between the bar 20 end the s rnnller rect-cognerframe. ln

Cl e

the drawings there are two such coils shown, an outer coik and an innercoil 241e, These coils are preferably connected in series, end currentissupplied thereto through the conductors 25, and 2G mounted in e.terminal boi: 2,7 suitably secured to the end Wall 12 ol the largerframe. A suitable non-niagnetic material such os babbitt 28 isinterposed between the upper edges of the Walls of the two 'frames esparticularly Shown in These upper edges of the two frames und also ofthe bar 22 are also preferably secured together by means of n0nmagneticmetal strips or bars 29 seated in' recesses 3l provided in the upperedges of thetwo frames `and the bar 22 and are suitably secured theretoby means ot countersunk screws Thus it will be seen that when the'chuckis assembled as obove described, the upper odg.. oi the walls of the twoframes andv also ol the central bar A22 will be llush with the uppersurface oit the.

bobbiit 2S und of the non-magnetic crossbars ln assembling this novel olick, the crossbors 29 are lirst secured to the edges ot the two 'framesand to the centrol bar 22, thereby retaining the Walls of the two tramesend the bar i n para llelspaced relation. The structure thus for:assembled is then plfced on a face plate or other smooth surface ...ithe bars 29 in contact therewith, after w h the babbitt is poured intothe rspaces between the walls of the two frames and of the bar 22,thereby positively sealing the upper portion of the chuck body againstleakage, as is clearly shown in Figure 9 Longitudinal c ooves 30 arepreteri ,c Y p ably provided ir. the wells or thetwo trames and inthejbgu 2; into which the molten babi muy w n `o i. cure v anchor i` 4oAie b tt lio tee l lU l tt tl weer the of@ ewes. ne im @c1523 are rthenAmounted 'in the. Chuck Y l g r te. scure o me 'o'toin the .lewe een .9Se d t` *l blt. edges of the twov trames by means oi? the oils orwindings in and from entering the body of the chuck withv the resultantdanger of short-c1rcuiting and thereoreburning out ot the coils, a`Suitable insulating medium such as oil is preferably introduced in thespaces wherein tie coils ere mounted, thereby completely subroerffingthe coils in an insulating oil with the result that it will bepractically impossible for any moistiu'e to c me Vinto Idirect contactwith the coils. To keep the body of the magnetic chuck completely'filled with oil, a gauge Si ispreferebly mounted in the end Wall 12 ofthe larger frame as particularly shown in Figures 2 and 5. rllhis gaugeis so arranged with respect to thechuck body that the oil level thereinwill be above the upper wall or portion of the chuck and therefore abovethe oil level therein, thereby creating a slight internal pressurewithin the chuck body. F or the purpose of i'naintaining the reservoirin vertical position, Whatever the worlzing position of the chuck, thereservoir is adjustahly connected with the delivery con duit as at 4l,so that the saine head or pressure can always be maintained Within thechuck and coil chambers.A A suitable duct or ducts 41.10 are lpro yidedin the wells oi the smaller rectangular 'freine of the chuck body inorder that the oil nay circulate between. the two vcoil chambers.

In the operation oA the magnetic chuck here showinthe chuck as a wholeis placed upon the usual reciprocating work table 35 oi an ordinarysurface grinder as shown in Figure l. ln this figure, the chuck is shownmounted onV the work table in a horizontal position beneath the grindingwheel 36, indicated in dotted lines. When it is desired to macnine orsurface-grind a number ofcastings or otherarticles, they will be placedupon the upper surface of the chuck es shown in Figure 2, each articlebeing eo `recaer? trames and of the central bar 22 which function aspositive and negative poles, the edges oit the walls 11, 12, 13 and 14@of the larger frame and also the upper edge of the central bar 22becoming the positive poles, and the upper exposed edges of the smallerframe becomingl the negative poles. Thus when a metallic article isplaced in contact with a positive and negative pole and current ispassed through the coils 23 and 24, :such article will be magneticallysecured to the iace of the chuck without danger of removal therefromuntil the flow of current through the coils 23 and 24- has beeninterrupted.

ln the operation of the chuck should a leak occur in the walls thereof',the internal pressure of the oil therein, caused by the oil level in thegauge 34. being above the level of the oil in the body of the chuck,will cause the oil to ooze or leak out of the fracture in the chuckbody, thereby preventing any water or moisture from entering therein andshort-circuiting the coil. Such leakage of oil from the chuck body willalso serve as a warming to the operator that the body ot the chuck hasbeen injured, and it will therefore be repaired before serious damagecan result. In addition to the oil within the chuck body functioning asinsulating medium for the coil and also to prevent moisture fromentering therein it also functions as a means ot holding' down thetemperature of the chuck when used continuously tor a long period oftime.

It desired, the chuck may be arranged on edge upon the reciprocatingwork table of the grinder as shown in dotted lines in Figure 1. `Whenthus positioned, the gauge 34 will be rotated a quarter of a turn fromthat shown in full lines in the same ligure, there by maintaining theoil level above the surtace of the chuck body. Lugs 37 are preterablyprovided on the end walls 11 and 12 of the larger frame or body of thechuck to provide means whereby the chuck may be securely clamped orfastened to the reciprocating work table 35 when positioned as shown indotted lines in Figure 1.

l claim as my invention:

1. A device of the class described, comprising a pair of pole 'tramesdisposed one within the otherl and spaced to provide an outer coilchamber between the trames, with the smaller frame providing an innercoil chamber, a reinforcing pole plate disposed medially of the innerframe, of less length than the iframe forming a coil support, a coilwithin each chamber, said outer frame having at its inner side adjacentone end, a cir-y cumferential groove, and said inner frame and poleplate having corresponding grooves on both sides, moldable materialforming plates sealingly closing and connecting the frames and poleplate by engagement within the grooves, and a work-engaging tace platedetachably fastened to the opposite side of, and closing the frame.

2. A hollow chuck comprising two pole frames, one within the other,spaced apart to provide two intercommunicating coil chambers, a poleplate disposed medially within the inner iframe, magnetic coils, one ineach chamber', the outer frame adjacent one side having a groove aroundits inner .tace and the inner trame and pole plate having thecorresponding grooves on both sides, and plates otmoldable non-magneticnaterial in sealing engagement with the grooves, and a work-engaging`plate detachably secured to and closing the opposite sides of thetrame.

3. A hollow chuck comprising two pole frames, one within the other,spaced apart to provide two intercommunicating coil chambers. a poleplate disposed medially within the inner trame, magnetic coils, one ineach chamber, the outer fra-me adjacent one side having a groove aroundits inner tace and the inner frame and pole plate having thecorresponding grooves on both sides, plates ot non-magnetic material inscaling engagement with the grooves, a work-engaging plate detachablysecured to and closing the opposite sides of the frame, and a supplyreservoir connected with the chuck and in communication with the coilchamber supplying oil for completely lilling the coil chamber,maintaining a head or pressure therein, and allowing expansion of theoil and in communication with the coil chamber supplying oil forcompletely iilling the coil chamber, maintaining a head or pressuretherein, and allowing expansion ot the oil when heated, during operationof the chuck, said reservoir adjustably arranged to be maintained invertical position whatever the working position of the chuck may be.

5. A reversible magnetic chuck, comprising a box-like chambered chuckbody. having a work-engaging plate detachably joined thereto closingthechamber on one side, a magnetic coil within the chamber, an oil deliveryconduit communicating with the chamber, and a combined oil reservoir andexpansion. chamber connected to, carried by ll l) and communieating`with the conduit and arranged at a level above the chamber for obtainingand maintaining ahead or pressure Within the chamber about the coil toprevent seepage of Water through a broken `joint in the coil chamber,whereby, if a joint in the chuck opens, the appearance of oil Willindicate a need of repair, While at the saine time Water is preventedfrom entering.

6. A magnetic chuck, comprising a plural piece chuck body including aWork-engaging plate detachably secured to and closing one side of thechuck having a plurality of interconiinunicating coil-receiving`chambers, an oil delivery pipe communicating With the chambers, an oilreservoir adjustably con nected with the oil pipe, and arranged abovethe level of the chamber for producing a head or pressure Within thechamber to prevent entrance of Water thereto by seepage, said reservoirmovable with the chuclr and adjustable to remain in vertical positionabove the chuck, Whatever the Working positionvo'il said chuck.

7. A magnetic chuck comprising frames one Within the other spaced toform coil chambers one about the other, and containing coils, pole barson one side transversely connecting` and securing the frames in spacedrelation, inoldable non-magnetic niaterial 30 sealinel closinp theraines about the bars and a face plate detachably secured to andV

